Studies in silazane chemistry

NASA TECHNICAL
MEMORANDUM

NAS\TMX-53I97

FEBRUARY 1, 1965

i

X

3*

in

STUDIES IN SILAZANE CHEMISTRY

by JAMES I). BYRD \NI) JAMES E. CURRY

Propulsion and Vehicle Engineering Laboratory

NASA

George C. Marshall
Space Flight Center,

Hunts ville, Alabama

WWcvo

ficfce

TECHNICAL MEMORANDUM X-53197

STUDIES IN SILAZANE CHEMISTRY

By

James D. Byrcl

and
James E. Curry

George C. Marshall Space Flight Center

Huntsville, Alabama

ABSTRACT ^ 5 9^^

The chemistry of a number of silazane compounds has been
studied in an effort to prepare polymers containing Si-N linkages.
This effort has resulted in the discovery or develppment of some new
and interesting polymeric materials.

Polysilazanes having good thermal stability, elastomeric prop-
erties,and good film-forming properties have been prepared, A
method has been developed for the preparation of an elastomeric
silazane from dimethyldichlorosilane and ethylenediamine. This
material has good thermal stability and remains rubbery after extended
exposure to elevated temperatures (300-400°C).

Polymers having a number of useful properties were prepared
by the polymerization of equimolar amounts of hexaphenylcyclotri-
silazane and a number of different aromatic diols such as p, p ! -biphenol.

ACKNOWLEDGMENT

Appreciation is expressed to Mr, J. K. Davis and
Miss Barbara Mrazek for their assistance in the prep-
aration and study of these polymers and to Messrs-
Albert C. Krupnick, John Barnes, Thomas H. Arnold,
Forrest T. Wells, C. L. Perry, D. H. Hamilton, and
J. W. Sims and Mrs. S. H. Corbitt of the Chemistry
Branch of the Materials Division for their assistance
in the analysis and characterization of these materials.
Appreciation also is expressed to Messrs. C. F. Smith,
F. Uptagrafft, J, H. Adcock, and Paul Pit-cock for
physical measurements data and to Mr. Harold Perkins
for his contribution tov/ard the success of this effort.
The interest and advice of Dr. Robert E. Burks of
Southern Research Institute is also acknowledged.

NASA-GEORGE C. MARSHALL SPACE FLIGHT CENTER

TECHNICAL MEMORANDUM X-53197

STUDIES IN SILAZANE CHEMISTRY

By

James D. Byrd

and
James E. Curry

MATERIALS DIVISION
PROPULSION AND VEHICLE ENGINEERING LABORATORY

TABLE OF CONTENTS

Pag*

SUMMARY 1

INTRODUCTION 1

STATE-OF-THE-ART 2

EXPERIMENTAL 3

Study of Hexaphenylcyclotiisilazane 3

Diamine -Silazane Polymers 3

Elastomers Derived from Silazanes 6

Polymers from Other Diamines 7

Cros slinking 8

Polymerization of Hexaphenylcyclotrisilazane in

the Presence of Diamines 8

Silazane-Triazine Polymer 9

Silazane-Diol Polymers 10

Silazane-Polyester 11

CONCLUSIONS , 12

REFERENCES 27

1 1 i

LIST OF ILLUSTRATIONS
Figure Title Page

1 Thermogravimetric Analysis of Cyclic

Trisilazanes 20

2 Differential Thermal Analysis of Hexa-

phenylcy clotrisilazane 21

3 Differential Thermal Analysis of Hexa-
phenylcyclotrisiloxane 22

4 Thermogravimetric Analysis of Ethyl-

enediamine- Silazane Polymer 23

5 Thermogravimetric Analysis of Silazane

Polymers 24

6 Thermogravimetric Analysis of Silazane

Polymers 25

7 Thermogravimetric Analysis of Silazane

Polymers 26

LIST OF TABLES

Table Title Page

I Composition °>f Heat-Barrier Samples 14

II Test Results of Heat-Barrier Samples 15

III Polymers from Dimethyldichlorosilane

and Organic Diamines 16

IV Polymers from Diphenyldichlorosilane

and Organic Diamines 17

V Polymers from Hexaphenylcyclotrisilazane

and Diol Compounds 18

VI Chemical Analysis of Polymers from Hexaphenyl-
cyclotrisilazane and Diol Compounds 19

i v

TECHNICAL MEMORANDUM X- 53197

STUDIES IN SILAZANE CHEMISTRY

SUMMARY

During recent years, a considerable interest has developed in
silazane chemistry- -the chemistry of silicon-nitrogen compounds.
A primary reason for this interest is the isosteric relationship between
the Si-O linkage of silicones and the Si-NH linkage of the silazane s,
which implies that there should be certain parallels in their chemical
behc ior. The silicones'have found many uses such as lubricants,
elastomers, and coatings.

This report summarizes the status of an internal study of the
chemistry of silazanes and of materials produced by various reactions
of silazanes. Most of this internal work was done in connection with
and in support of contract NAS8-1510 with Southern Research Institute.

These combined efforts have shown that polysilazanes have many
interesting properties, including good thermal stability and good film-
forming properties, especially with respect to their stability in
: extreme environments. Certain polysilazanes can be prepared as weak
elastomers in a one-step polymerization. These elastomer gums have
potentially useful properties after thermal curing.

INTRODUCTION

Silicones i . their various forms have found wide application in
materials and chemical technology. They have shown many improved
properties in comparison to conventional organic materials. However,
they have certain limitations. Specifically, they are limited in their
utility at high and low temperature extremes. Generally, silicones do
not withstand prolonged exposure at temperatures above 250°C (482°F),
and the best silicone elastomers become rigid at approximately -130°C
(-202°F).

Since the N-H group of the silazane is isoelectronic with the sili-
cone oxygen atom, it seems logical that the silazanes should be studied
in an effort to obtain materials with improved properties. The silazane
offers the potential advantage of being able to react or crosslink at the

hydrogen atom which is attached to the nitrogen atom. Another theoreti-
cal advantage of the silazanes is the a ir -pir interaction between the
silicon and nitrogen atoms. This e suits from the ability of the
"unshared" pair of electrons o f ne nitrogen atom to interact with the
empty d orbitals of the sili^ - A which causes a shorter bond distance.
This is also an advanta^ ±n terms of chemical stability because the
Si-N bond is render (ess subject to nucleophilic attack in many cases.

Some of the silazanes tend to be hydrolytically unstable. However,
with the proper substituents attached to the silicon and nitrogen atoms,
the dir -pTt bonding character may be increased, thus increasing the
hydrolytic stability. By Lhe use of suitable processing and curing
techniques, this instability may also be minimized.

STATE-OF-THE-ART

The study of silicon-nitrogen compounds dates back to 1889 when
Reynolds (Ref. 1) reported the preparation of tetraaminosilanes.
However, the bulk of the work on polymeric silicon-nitrogen compounds
has been done within the past 20 years. During this period, the interest
in compounds of this type has become extensile. In 1961, Fessenden
and Fessenden (Ref. 2) published a comprehensive review of silicon-
nitrogen chemistry which cited a total of 221 references on. these
materials. Concurrently, a considerable interest iaj developed in
producing polymers containing silicon-nitrogen units. In 1959,
Henglein and Lienhard (Ref. 3) reported polymers of the type £si(CH3)--
NH-fCH?) "NHI ' prepared from the reaction of dimethyldichloro-
silane with various diamines. Also, shortly afterwards, Minne' and
Rochow (Ref. 4) independently reported the same polymer and showec
how it coordinates with several metal chlorides. In the meantime,
work was funded by this organization (starting in 1959 as a U. S. Arir»y
contract) to investigate methods of preparing polymers containing
silicon-nitrogen bonds (Ref. 5). This eifort resulted in the devel »p? , u
of some interesting materials, and it has beer, continued and expands t\
(Contract NAS8-1510) (Ref. 6).

To supplement and assimilate the work done under contrac: ;< us,
an internal investigation on silicon-nitrogen polymers has beer conducted
within our own laboratory. This report summarizes the present status
of our work in relation to the contracted program.

EXPERIMENTAL
Study of Hexaphenylc yclotrisilazane

Burks and coworkers (Ref. 5 and 7) found that certain cyclic

silazanes, such as hexaphenylcyclotrisilazane, may be polymerized
to infusible polymers with exceptional thermal and chemical stability.
In an effort to learn more about the complex high temperature reactions
leading to the iormation of this intractable polymer, hexaphenylcyclo-
trisilazane was investigated by differential thermal analysis (DTA) and
thermogravimetric s,nalysis (TGA).

The thermal behavior of hexaphenylcyclotrisilazane as revealed by
TGA is compared to that of the corresponding siloxane in PIG i. DTA
studies of the same two materials are shown in FIG 2 and 3.

The good thermal stability of the ultimate product and the strong
endothermic character of the high temperature reactions of hexaphenyl-
cyclotrisilazane indicate that this material may be a useful component
of ablative oi intumescent coatings.

Several tests have been made to assess the performance of this
matenal in heat barriers. Six samples containing varying amounts of
hexaphenylcyclotrisilazane were tested by exposure to a radiant lamp
at 24 BTU/ft 2 /sec for 1Z0 seconds while being vibrated at 30 cycles
per second with displacement of 0. 25 inch with an acceleration of 1 1
times gravity.

The back-face temperature rise was measured as an indication of
the materials performance. The samples were prepared by Southern
Research Institute under Contract NAS8-1510 (Ref. 6), and tests were
made at this Center. Tb^ compositions of the test samples are shown
in Table I, and the test results are given in Table II. It is evident that
some improvement resulted since the back-face temperature after 120
seconds was only 62. 2 C for the sample with 25% hexaphenylcyclotri-
silazane as compared to 90. C for the sample containing no silazanc.

Diamine-Silazane Polymer-

Extensive effort (Ref. 3, 4, 5, 8, 9, 10, 11, 12, 13, and 14) has
been expended on the study of clichlarosiiane-organic diamine copoly-
merizaticn reactions.

The reaction product of ethylene diamine, En(NH?)2> anc ' dimethyl-
dichlorosilane, Me2SiCl2 , ha.-, been stu 'ied extensively; three poly-
meric structures are possible:

Me H

I I

I Linear-4-Si — — « N
I

Me

En

H
I

N.

n

Me
I
II Cyclic-f-Si

J

Me

En

r tn i

Me Me

HI Ladder

Me

i.

Me

Me
I
-Si -

I

Me

N

n-n

• N.

Minne and Rochow (Ref. 4) originally reported that the linear form is
iirr.t obtained and that it can be converted to the ladder form by reflux-
ing in the presence of copper (II) chloride or beryllium chloride. Hew-
ever, in a later report (Ref. 15), Kruger and Rochow report that these
polymers contain five-membered ring systems (Type II) which are
connected by silicon atoms rather than having the exclusive linear struc-
ture (Ref. 10). Breed and coworkers (Ref. 11, 13, and 14) have
reported polymers which are believed to have the cyclic configuration,
and they have actually isolated monomeric species containing the five-
membered ring moiety. In all of these cases, it was necessary to
perform a two- or three-step reaction to obtain a product having an
analysis which suggested the linear and/or cyclic structure.

Our work has led to a one- step method for obtaining vv'iat appears
to be a high proportion of cyclic and/or ladder polymer configuration.
It was found that the reaction of a 1:1:2 molar ratio of dimethyldichioro-
silane, ethylenediamine, and triethyiamine produced a spongv elasto-
meric polymer during the initial step. A typical reaction was conducted
by adding 0. 2 mole of dimethyldichiorosilane and ZOO mil of dry benzene
to a one-liter, three-neck flask which was equipped with a stirrer,
dropping funnel, and reflux condenser. A separate solution was pre-
pared containing 0. Z mole of ethylenediamine and 0. 4 mole of triethyi-
amine in 100 ml of dry benzene. The mixed amine solution was added
by drops over a 90-miuute period to the halosilane. The resulting
solution was then refluxed for a period of 3-1 /Z hours. The triethyi-
amine hydrochloride was removed by filtration, and the benzene was
removed under reduced pressure. This gave 97% yield of a soongy
yellow solid polymer. The calculated analyses of the three possible
polymer forms compared to experimental values are shown below:

Calculated Values Actual

Linear Cyclic Ladder Experimental

% Nitrogen 24. 10 16. 25 16. 25 16. 8

% Silicon 24. 16 32. 59 32.59 31. 5

The carbon and hydrogen contents of all three forms are so close
that they are valueless for characterization purposes, and the situation
is complicated further because the cyclic and ladder forms have identical
silicon and nitrogen contents. Thus, it can be inferred only that this
particular polymer was comprised largely of cyclic and/or ladder units.
The elastomeric nature of the product suggests strongly thai appreciable
ladder-type bridges occurred as crosslinks between chains. However,
it is concluded that the use of fcriethylan.ine as an acid acceptor in the
above system produced a polymer with potentially useful elastomeric
properties.

To compare the properties of the prouuet with and without triethyi-
amine, experiments also were made where no triethyiamine was used.
In an experiment of this type, using 0. 2 mole of dimethyldichiorosilane
and 0. 6 mole of ethylenediamine, a slightly viscous light-yellow liquid
was obtained. The elemental analysis of this material indicates a

mixture of the linear and c/clic form. This is shown in the follow-
ing table:

Theory For
Linear Form Cvclic/ Ladder Found

% Nitrogen 24, 14 16.25 16. 8

% Silicon 24. 14 32. 59 26. 2

Based on the silicon analysis, a mixture of about 75% linear and about
25% cyclic and/or ladder is formed in this case.

This work also has shown that other bases such as sodium bicar-
bonate may be :\sed as acid acceptors in the reaction of dichlorosilanes
with diamines.

Elastomers Derived from Silazanes

A polyethylenediaminesilazane was prepared according to the pro-
cedure given above where triethylarnine was used as the acid acceptor.
After the by-product (hydrochloride salt) was lemoved, the solvent
was evaporated to give a "dope M containing about 67% solids. A film
was cast on an aluminum plate by using this thick material. The solvent
was removed by heating at 70 C for 18 hours, and the resulting film was
cured at 204 C for two hours and then at 3l5°C for one hour. This
resulted in a smooth, elastomeric coating which could be peeled from
the plate. The film did not appear to be veiy strong, but it was very
elastic. It remained unchanged in physical appear; nee and retained its
elasticity after standing for 17 months under normal atmospheric con-
ditions. After this period, the nitrogen analysis of different areas of
the same sample ranged from 0. 3 to 13. 9% which indicated a hetero-
geneous composition. This compared to 16. 8% nitrogen in the original
starting material. This elastomeric material had a smooth, uniform,
nonporous surface, and the elastomer was almost transparent. Thicker
(I /4-inch) layers of the same material were cured at 400 C in two
separate beakers, for one hour in one case and two hours in another.
The nitrogen content ranged from 4 to 10% after being cured. The
v 'eight loss ranged from 50 to 58%, and the final product was a black
foamed solid which was very elastomeric but weak in strength.

It is concluded that siiazane polymers of this type ma/ be cured to
weak elastomers, and, during the curing process, a variable propor-
tion of the initial Si-N bonding is converted to Si-O bonds. However,
the remaining nitrogen content appear? to be significant in. contributing
to the properties of material.

Figure 4 shows a thermogravi metric analysis of the polymer before
and after curing, Although the thermal stability is not as good as some
of the newer high temperature polymers, this cured silazane-derived
material has an attractive degree of thermal stability.

Polymers from Other Diamines

Several other- polymers of this type were prepared oy reacting
dimethyldicholorosilane with various organic diamines. The diamines
used included i, 3-propanediamine, 1 T 6-hexanediamine, 1, 4-phenylene-
diamine, piperazine, benzidine, 4, 4 1 -methylene -dianiline, and 4,4'-
oxydianiline. The results and data on these runs are summarized in
Table III. The physical form of these polymers included foamed elas-
tomers, rigid foamed solids, powcers, waxes, and viscous liquids.
Their engineering properties are being investigated presently.

Another series of polymers was prepared by reacting diphenyldi-
chlorosilane with four different organic diamine compounds. The
diamines used in this case included ethylenediamine, 1, 6-hexanedia-
mine. 1, 4-phenylenediamme, and piperazine. The data on these polymers
are summarized in Table IV. The physical forms of these polymers
ranged from tacky gels to brittle solids. The usefulness of these mate-
rials is still under study.

The nitrogen portion of both the phenyl and methyl substituted
polymers appears to be somewhat unstable in the atmosphere. An
example of this is a case where the diphenylsilane- ethylenediamine
polymer was allowed to stand in the air at room temperature overnight
and was then placed in ah air circulating oven at 250°F for one hour,
and then at 400°F for 45 minutes. The elemental analysis of this
material is shown before and after heating.

Found

B

efore

Heatin-

Aft

er Heating

% Carbon

71.

8

72. 6

% Hydrogen

6.

D

5. 5

% Nitrogen

8.

3

1.4

% Silicon

11.

4

14. 1

Unaccounted

1.

9

6. 4

Theory

70.

00

6.

67

11.

67

11.

66

It s" oi. ' be noted thci f the nitrogen content dropped from 8. 3% to 1. 4%
up^ heating in air.

Crosslinking

A number of attempts were made to improve the strength of che
cured silane -diamine polymers. The only material that showed any
promise was trichlorosilane. When 10% of the dimethyldichlorosilane
'was replaced by trichlorosilane, a significant improvement in strength
of the product was noted. The use of 25% of the trichlorosilane did
not appear to increase the strength further. MOCA, (4, 4 ( -methylene -
bis-(2-chloroaniline) , benzoyl peroxide, and AIBN {a , a ' -azodii sobuty-
ronitrilc) wore not effective as cross-linking agents.

Polymerization of Hexaphenycyclotrisilazane in the Presence ji
Diamines

Several attempts were made to copolymerize three different amine
compounds with hexaphenylcyclotrisilazane by the catalyzed amine
exchange reaction. An example of this type reaction is shown as follows:

Ph Ph

\ /

Si

HN

/ \

NH

Ph

Ph

\

/

Ph

Sx Si

Ph

N
H

+ 3 H 2 N-Et-NH 2

Ph H H

.Si N Et— N

I
Ph

III \

— Si N Et— N -y 3n NH ? J

NH4SO4

Quinoline

n

Ph represents a phenyl group.

The runs were made by using hydrazine, ethylenediamine, and ethanol-
arnine in quinoline. Ammonium sulfate was used as the catalyst. In
each case, the following portions were used:

Hexaphenylcyciotrisila^ane
Amine

Ammonium Sulfate
Quinoline

0. 017 mole
0. 03-4 mole
0. 0019 mole
2 ml

These were heated at about 240°C for 12 to 15 hours. The salts were
then removed by filtration, and the polymer was recovered after
removing solvent and unreacted amine under reduced pressure. In
each case, the product obtained was a hard, glassy solid. Fibers could
be drawn from the melt of the ethylenediamine polymer. The prelimi-
nary results indicated that the polymers obtained by this route are
superior in some respects to those obtained by the halosilane-amine
route. Perhaps the main reason for this difference is the elimination
of the use of hydrolytically unstable halosilane as an intermediate.

S iiazane-Triazine Polymer,

A polymer was prepared by the reaction of equal molar amounts of
:diphenyldichlorosilane and 2, 4-amino-6-phenyl-s-triazine using triethyl
amine as the acid acceptor. A 74% yield of a soft, yellow polymer
was obtained. Although it was not possible to fully characterize this
polymer, it is believed to have the following structure:

Ph

I

C

Ph

I

-Si

I
Ph

H

N

/

<s

N

H

N - C C - N~

n

Ph represents a phenyl group.

This silazane-triaisine structure should have outstanding thermal stability,
and this is being studied further.

Siiazane-Diol Po lymers

Among the most interesting polymers investigated during this study
were those obtained by the reaction of hexaphenylphenylcyclotrisila-
zane with equimoL.r proportions of various diols. An example of this
reaction is shown below:

I

Ph Ph
\ /

Si
/ \
IN NH

+

HO-/C

Ph

\

S

i

i Si

\n/

'/ Ph

\_

H

"Ph H

Ph

H

Ph

1 1

1

1

1

-Si N-

_Si —

- N

-Si

1

Ph

\

Ph

1

Ph

<cH5>°h

o

-##<>

n where Ph

represents a. phenyl group.

Breed and Elliott (Ref. 13 and 16) have also reported polymers
prepared by this method. During this study, we prepared copolymers
of hexaphenylcyclotrisilazane with eight different d.ols. The diols
included ethylene glycol, 1, 6-hexanediol, hydroquinone, 4, 4' -biphenol,
2, 2-propane-bis(4-hydroxybenzene;. 4, 4' -dihydroxydiphenyl ether,
2, 7-naphthalenediol, and diphenylsil?nediol. Each diol produced a
polymer having an empirical analysis consistent with the following
general formula:

Ph

I
■vSi -

I
Ph

H Ph H Ph
I ! I I

N — Si — N - Si - O - R- O--

Ph

Ph

n

10

where R represents one of the diol groups mentioned above and Ph
represents a phenyl group. A description of the physical form and
fiber and/or film forming character of these materials is given in
Table V, and the elemental analyses are given in Table VI. The
thermal stability of each of these materials is shown in FIG 5, 6,
and 7. It may be observed that the best of these are stable to about
500°C (°32°F). Some are elastomeric solids, and others form tough
semiflexible films arid fairly strong fibers.

A number of polymers which are not silazane polymers but which
were made by using a silazane as one of t**e starting materials have
been reported (Ref. 17 and 18* by the authors.

Silazane -Polye ster

A silazane containing polyester was prepared by the melt con-
densation of equal molar quantities of hexaphenylcyclotrisilazane and
terephthalic acid. This produced a polymer believed to have the
following structure:

Ph

H

Ph H Ph

O

o .

1

1

1 1 1

* /

?3S"

Si

N —

_ Si N — Si O-

-cfl

3)c-o

I

1 1

\

±y

Ph

Ph Ph

n

where Ph represents a phenyl group. The product was a light yellow
polymer which gave brittle fibers from the polymer melt. This
material had the following analysis:

Element Found Calculated

% Carbon

% Hydrogen

% Oxygen

% Silicon

% Nitrogen

70.

1

4.

2

8.

7

11.

1

2.

7

71.

31

4.

90

8.

67

11.

37

3.

78

11

Since only ammonia is a by-product of this reaction, the polymeriza-
tion process is simple and straightforward. A full assessment of the
properties of -this material will be undertaken.

CONCLUSIONS

The differential thermal analysis of hexaphenylcyclotrisilazane
revealed two strong endothermic bands which peaked at about 230° C (melt-
ing point 213-215°C) and 550°C, with three additional minor endothermic
peaks at approximately 590, 700, and 860°C. The endothermic nature of
these changes indicates that this material may be useful as a component in
heat-barrier construction. Although there is considerable scatter in
the data, there is an indication that the hexaphenylcyclotrisilazane
improved the effectiveness of the heat-barrier. The backface tempera-
ture rise ranged from 90°C without any hexaphenylcyclotrisilazane to
62°C v/ith 25% hexaphenylcyclotrisilazane. The sample thickness loss
ranged from 98 mils with no hexaphenylcyclotrisilazane to 53 mils with
10% hexaphenylcyclotrisilazane.

A one -step method has been developed for the preparation of a
solid foamed elastomer from the reaction of dimethyldichlorosilane
and ethylenediamine. This material subsequently has been cured into
a stable, transparent, elastomeric film having low strength but attrac-
tive thermal stability. A number of related polymers were prepared
by reacting dimethyldichlorosilane with other organic diamines. An
analogous series of polymers with phenyl substitution on the silicon
atoms was prepared by the reaction of diphenyldichlorosilane with
organic diamines,. When cured at 400°C, these materials form very
stable elastomeric products. A considerable amount of Si-N bonding
is converted to Si-O bonding during the curing process. However, it
is concluded that the amount of Si-N bonding remaining plays a signifi-
cant part in the properties of these materials.

A number of attempts to improve the strength of the cured elasto-
mers has resulted in slight increases in strength. However, this
increase has not been of sufficient significance to produce a material
with outstanding engineering properties.

A number of potentially useful polymers was prepared by chain
opening reactions between equimolar amounts of hexaphenylsilazane and
various diol compounds. Some of these materials have good film and

12

fiber -f or. ning properties. The best of these materials is stable to
about 500 °C and undergoes a total weight loss of about 45% during
heating to 900°C.

An interesting new polymer which contains the triazine ri$Lg was
prepared by linking the rings through the -N-Si-N- linkage. Many
possible variations exist for polymers of this type.

A polymer containing polyester units along with silicon-nitrogen
bonds was also prepared.

These exploratory studies have served to demonstrate the many
different typ s of silazane polymers that are within reach by established
synthetic routes. These materials are characterized by high thermal
stability and varying degrees of hydrolytic instability. The utility of
simpler silazane compounds as synthetic intermediates has also been
demonstrated by thio work.

Continued study of these materials as high temperature or intumes-
cent coating constituents is indicated. An evaluation of the more
promising elastomeric materials derived from silazanes will also be
attempted.

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o 60
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70
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480°C 540°C

100 200 300 400

TEMPERATURE °C

I HEXAPHFNYLCYCLOTRISILAZANE
H HEXAPHENYLCYCL0TRISIL0XANE

500

600

FIGURE I THERMOGRAVIMETRIC ANALYSIS OF CYCLIC TRISILAZANES

20

w

<
N
<J

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DIWM3H10X3-

OIWM3H10aN3

400

600

800

1000

TEMPERATURE °C

I CURED
D UNCURED

FIGURE 4- THERMOGRAVIMETRIC ANALYSIS OF ETHYLENEDIAMINE-
SILAZANE POLYMER

23

10

20

30

40

50

« 60 -
o

UJ

70

80

90

100

I.

II.

III.

200

— Q

-L

400

TEMPERATURE

O -

~o-©-o- -

Ph

I
Si

I
Ph

Ph

1
Si

I
Ph

600
°c

Ph

I
Si

I
Ph

H

I
N

H

I

N

eoo

H

I

M

Ph

i

Si
I
Ph

Ph

I

Si

I

Ph

Ph H

I I
Si- N

I
Ph

K
I

N -

N

Ph represents a. phenyl group,

FIGURE 5. THERMOGRAVIMETRIC ANALYSIS

1000

Ph

I
- Si +
I
PhJ n

Ph

I

Si4-

Ph

Ph

I
Si ■

I
Ph

n

n

24

10

20

30

40

*p 50

vt
<n

3 60

x
e

u 70

80

90

too

III.

200

400 600

TEMPERATURE °C

O -

Ph
\

Si -

i

Ph

H

600

Ph
l

Si -

i
Ph

1000

N

II.

CH 3 W

Ph

Si -
i

Ph

H
i

N

Ph

N

Ph
i

Si--

l
Ph :

P fi

. Si—
I
Ph

n

Mi
I

°"© )U °^0^° * S f "

f

H Ph H
I I I

N - Si - N - Si
l i

?h Ph J

n

Ph represents a phenyl group in each case.
FIGURE 6. THERMOGRAVIMETRIC ANALYSIS

25

I. -o -

Ph

I
Si -

I
Ph

200

400 600
TEMPERATURE °C

800

O -

Ph H

si 4

I

Ph

II. --0 - (CH 2 ) 6 - O -

IU.-.0 - (CH 2 ) 2 - O

Ph
i

Si
i
Ph

Ph

Si
i

Ph

p i h

- Si -
I

Ph

¥

H
I

N

P , h

Si

i

Ph

P , h

Si
I
Ph

Ph
I

Si-
I

Ph

H
I

N

¥

n

Ph

Sii"

I
Ph

Ph
i

Si"
i

Ph

n

n

Ph represents a phenyl group in each case,
FIGURE 7. THERMOGRAVIMETRIC ANALYSIS

1000

26

REFERENCES

1. Rey- uds, J. E. , Journal of The Chemical Societ y, 55. 475 (1889).

2. Fessenden, R. and Fessenden, J. S , Chemical Reviews , 61, 361
(1961),

3. Henglein, F. A. and Lienhard, K. , Ma kromolek^are Ci^mie, 32,
218 (1959).

4. Minne, R. N. and Rochow, E. D. , "Coordination of Polymeric
Organosilyl Amines. I. Reactions with Copper (II) Ion, " Joxirnal
of the American Chemical Society , 82, 5625 (I960).

5. Burks, R. E, and Ray, W. R. f "A Study of Polymers Containing
Silicon Nitrogen Bonds, " Contract DA-01 -0009-506-ORD-829,
Summary Technical Report, Dec. 1, 1959 to Jan. 31, 1961,
Southern Research Institute.

6. Burks, R. E. and Ray, T. W. , ,! A Study of Polymers Containing
Silicon-Nitrogen Bonds, M Contract NAS8-1510, Three Annual
Summary Reports, Feb. 4, 1961 to April 3, 1964, Southern
Research Institute.

7. Burks, R, E, , Jr., Lacey, R. E. , Lacey, J. C. , and Ray, T, W. ,
"Conversion of Hexaphenylcyclotrisilazane and Related Materials

to Infusable Polymers and Coatings, l! Southeastern Regional Meeting
of The Ameri :an Chemical Society, Charleston, West Virginia,
October 16, 1964,

8. Ibid p, 56<:3

9. Minne, R. N. , "Organosilicon Coordination Polymers, u Contract
No. Nonr-1866(13), May I960, Harvard University.

10, Contract Nonr- 1866(13), Eight Reports from September 1961 to
September 1963.

11. Breed, L. W. , Elliott, R, L. , and Farris, A. F. , "Preparation
and Polymerization of 1, 5-Diamino-2, 4-alkylenetrisilazanej, "
Journal of Polymer Science , 2, 45(1963),

27

REFERENCES (Concluded)

12. "Linear Si-N Polymers Prepared, ,f ChemicaJ and Engineering
News, 42, 26, Jan. 6, 1964.

13. Breed, L. W. and Elliott, R. L. , "Synthesis of Elastomers
Containing Si-N Bonds in The Main Chain, n Contract No. DA-23-
072-ORD-1687, Three Summary Reports from June 1961 to
December 1963.

14. Breed, L. W. , Zlliott, R. L. , and Ferris, A. F. , "Organosilazane
Polymers, fl Journal of Organic Chemistry , 27, 1 114, (1962).

15. Kruger, C. R. and Rochow, E. G. , "Polyorganosilazanes, "
Journal of Polymer Science: Part A , 2, 3179 (1964).

16. Elliott, k. L. and Breed, L. W. , "Polymers from Cyclosilazanes
and Organic Diols, " 148th National Meeting of The American
Chemical Society, Chicago, 111., Aug. 30 to Sept. 4, 1964.

17. Curry, J. .E. and Byrd, J. D. , fl Silane Polymers of Diols, ,f
NASA TM X-53028, April 6, 1964.

18. Curry, J. E. and Byrd, J. D. , "Silane Polymers of Diols, lf
Journal ol Applied Polymer Science, in press.

28